I think it is important to have a national system.
At GCSE and A Level we have a national system and no one expects schools to develop their own ways of measuring attainment at that point. I suspect that most parents couldn't say what an A at GCSE in Biology, or a C in Maths means, in terms of what they can do - this doesn't limit their usefulness,for children, parents and employers.
However,frequently the reasoning that is trotted out (and has been on this thread) against national expectations or measurements, is that they don't tell parents what their child can do.
To anyone who says that it is irrelevant where a child's attainment lies in terms of national expectations, but the only thing that matters is their own progress, I say ROT! It DOES matter. Being below national expectations at a certain point does not mean someone's life is ruined or they can never progress or be happy, but if someone fails to achieve a solid range of GCSEs then their life chances in terms of work are limited. And being on track for that kind of outcome can be indicated from national approaches to tracking and interventions can then be applied to try to improve outcomes.
If all schools adopted a system where they talked about the NC for that year and used the terms emerging, expected, exceeding, then parents would have some kind of idea. This isn't even uniform now though. Even if it were! if a child is reported to parents as emerging, it isn't clear to the parents if they are slightly behind national expectations or far far behind. And I do think parents need to know that....and the old NC levels did give more of an indication of that......similar to knowing a D at GCSE wasn't a fail by much, whilst an F was a fail by a long way.
And surely in terms of government tracking of progress, schools have to feed information into a system which uses nationally accepted measures. Yes I know only Yr2 and Yr6 reporting is compulsory yada yada yada, but we all know that as schools used to break down the steps of progress required at KS2 into unofficial points to reach at the end of each year,to be on track for L4 or 4B or whatever, this will still happen in some form, even if schools all develop their own versions, which parents are not privy to. I don't believe for one moment that any school will not have a measurement for what a child needs to be at, for each year of primary schooling, in order to be on track to meet government minimum guidelines......and hence in doing that, they will also be tracking those performing above And below, and not just by the terms emerging or exceeding, but in terms of greater breakdown than that.
And children will continue to be set in Year 7, and GCSE predictions to be based on what they achieved at the end of KS2, in the same way that predictions of KS2 outcomes will be based on KS1 outcomes.........the info is all there......parents just want to know.
Again, I return to the point that parents don't need to know what a B grade at GCSE involved or what an A at A level involved knowing, for it to be useful. What they can take from it (in advance of results and after them) is the next options that are available given those results - and that is really important. So they know if A Levels are sensible at 16, if an apprenticeship might be viable, if applying to a Russell Group Uni is viable or daft. And knowing about attainment relative to national expectations delivers the same kind of useful information for all children from the start of school until the end.